Conventionally, various types of apparatuses are knows as a liquid processing apparatus that performs a liquid processing such as cleaning, etching, plating, or developing of a substrate such as a semiconductor wafer (hereinafter, also referred to as a wafer) by supplying a processing liquid to a surface or a rear surface of the substrate while rotating the substrate held in a horizontal state. See, for example, Japanese Patent Application Laid-Open No. 2009-94525 which discloses a single wafer type liquid processing apparatus in which the processing liquid is supplied to the surface of the substrate rotated and held by the spin chuck, thereby processing the substrate one by one. In the single wafer type liquid processing apparatus, a technology has been known where a fan filter unit (FFU) is installed at an upper side of a processing chamber to deliver a gas such as nitrogen (N2 gas) or clean air from the FFU to the processing chamber in a down-flow mode.
A configuration of the liquid processing apparatus where the FFU is installed at an upper side of a processing chamber will be described with reference to FIGS. 11 and 12. FIG. 11 is a side view illustrating a schematic configuration of a conventional liquid processing apparatus and FIG. 12 is a plan view of the conventional liquid processing apparatus shown in FIG. 11. As shown in FIGS. 11 and 12, the conventional liquid processing apparatus 200 includes a processing chamber (chamber) 210 in which a wafer W is received and liquid processing of received wafer W is performed. As shown in FIGS. 11 and 12, a holding unit 220 that holds and rotates wafer W is installed in processing chamber 210, and a cup 230 is disposed around holding unit 220. In conventional liquid processing apparatus 200, a nozzle 240 that supplies a processing liquid from an upper side of cup 230 to wafer W held by holding unit 220, and an arm 241 that supports nozzle 240 are installed in processing chamber 210. An arm supporting portion 242 which extends substantially vertically is installed at arm 241 to support arm 241. Moreover, arm supporting portion 242 is rotated by a driving mechanism (not shown) forwardly and reversely. As a result, arm 241 is rotatable about arm supporting portion 242 forwardly and reversely, and is rotatably moved about arm supporting portion 242 between an advance position (see a solid line in FIG. 12) where a processing liquid is supplied to a wafer W held by holding unit 220 and a retreat position (see an alternate long and two short dashes line in FIG. 12) where arm 241 is retreated from cup 230 (see an arrow in FIG. 12).
As shown in FIG. 11, a fan filter unit (FFU) 250 is installed at the upper side of processing chamber 210, and gas such as nitrogen (N2 gas) or clean air is delivered from FFU 250 to processing chamber 210 in a down-flow mode at all times. An exhaust unit 260 is provided at the bottom of processing chamber 210 and an atmosphere in processing chamber 210 is exhausted through exhaust unit 260. As described above, gas such as clean air is delivered from FFU 250 to processing chamber 210 in the down-flow mode and the gas is exhausted through exhaust unit 260 to substitute the atmosphere in processing chamber 210.